Power converter with output voltage level indicating device

ABSTRACT

A power converter with output voltage level indicating device is disclosed. The power converter includes a casing, an interior of which is disposed with a control circuit. The control circuit includes a feedback circuit and a DC-to-DC conversion circuit. The feedback circuit is coupled to the DC-to-DC conversion circuit and connected to a level-selecting terminal by at least one resistor to provide a feedback signal to the DC-to-DC conversion circuit which in turn changes the voltage level of the DC output. An output socket is formed at the casing, which is connected with the control circuit. The output socket includes two primary, power terminals and at least one secondary, level-selecting terminals. A level-selecting terminal device is connected to the output socket via an extension cable for getting the DC voltage and supplying the DC voltage to an appliance via an output terminal. A display device is provided at the casing for showing the output voltage level to the output terminal of the level-selecting terminal device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a power converter, and inparticular to a power converter comprising an output voltage levelindicating device for indication and easy reading of output level ofvoltage.

2. Description of the Prior Art

Portable electronic appliances, such as mobile phone and notebookcomputer, play an important role in the modern world in doing businessand society activities. Such portable appliances are often powered bybuilt-in power sources, which must be constantly recharged in order tomaintain operability of the portable appliances. Also, external poweringis also available for most of the portable appliances, such as walloutlet, automobile electrical system including cigarette lighter socketand electrical socket regularly available in airplanes. Often theexternal powering must be converted by for example a conversion circuitmade in the form of an adaptor before it can be supplied to the portableappliances.

However, the portable appliances are often operated with differentworking voltages and for such a reason, the general consumers that ownand use two or more different portable appliance must regularly bringtwo or more adaptors corresponding to those portable appliances. Thiscomplicates the use of the portable appliances and is very troublesometo the consumers. U.S. Pat. No. 6,628,535, issued to the presentinventor, teaches a power converter that provides selectable outputvoltage levels to different appliances or loads. The power converter ofthe '535 Patent comprises an output to which a terminal connector isselectively coupled. The terminal connector comprises a circuitcomprised of resistors that generates a feedback signal to a controlcircuit of the power converter, inducing a corresponding voltage levelat the output of the conversion device.

Such a conventional power converter works well in supplying voltage ofdifferent levels to electronic appliances that operates with differentworking voltages. It, however, is still unclear to a user what voltagelevel is being output by the power converter when the device is poweringan electronic appliance. This may cause problem to the user.

Thus, the present invention is aimed to provide a power converter thatovercomes the drawback of the conventional devices.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a power converter thatis capable to display the output voltage level. The power convertercomprises a display device for showing the voltage level at the outputterminal of the level-selecting terminal device.

Another object of the present invention is to provide a portable powerconverter with output voltage level display device. The power converteris engageable with various level-selecting terminal device. By means ofthe display device, the output voltage level at the output terminal ofthe level-selecting terminal device is shown.

To achieve the above objects, in accordance with the present invention,there is provided a power converter with output voltage level indicatingdevice. The power converter includes a casing, an interior of which isdisposed with a control circuit. The control circuit includes a feedbackcircuit and a DC-to-DC conversion circuit. The feedback circuit iscoupled to the DC-to-DC conversion circuit and connected to alevel-selecting terminal by at least one resistor to provide a feedbacksignal to the DC-to-DC conversion circuit which in turn changes thevoltage level of the DC output. An output socket is formed at thecasing, which is connected with the control circuit. The output socketincludes two primary, power terminals and at least one secondary,level-selecting terminals. A level-selecting terminal device isconnected to the output socket via an extension cable for getting the DCvoltage and supplying the DC voltage to an appliance via an outputterminal. A display device is provided at the casing for showing theoutput voltage level to the output terminal of the level-selectingterminal device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be apparent to those skilled in the art byreading the following description of preferred embodiments thereof, withreference to the attached drawings, in which:

FIG. 1 is a perspective view of a power converter constructed inaccordance with a first embodiment of the present invention withconnection cables detached therefrom;

FIG. 2 is a block diagram of a control circuit of the power converter ofFIG. 1;

FIG. 3 is a block diagram of a DC voltage level indicating circuit ofFIG. 2;

FIG. 4 is a perspective view of a second embodiment of the powerconverter in accordance with the present invention;

FIG. 5 is a block diagram of the control circuit of the power converterof FIG. 4;

FIG. 6 is a perspective view of a third embodiment of the powerconverter in accordance with the present invention;

FIG. 7 is a perspective view of a fourth embodiment of the powerconverter in accordance with the present invention;

FIG. 8 is a perspective view of a fifth embodiment of the powerconverter in accordance with the present invention;

FIG. 9 a block diagram of the control circuit of the power converter ofFIG. 8; and

FIG. 10 is a perspective view of a sixth embodiment of the powerconverter in accordance with the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings and in particular to FIG. 1, a powerconverter constructed in accordance with the present invention,generally designated with reference numeral 100, comprises a casing 1. Aplurality of rechargeable batteries 2 are disposed in an interior of thecasing 1, which is used for supplying a DC voltage.

The casing 1 is provided with an input socket 11 with which a plug of apower cord connecting to a power source (not shown) is engageable forcharging the rechargeable batteries 2. The casing 1 is formed with anoutput socket 12 for connecting to a device-side plug 31 at one end ofan extension cable 32. A circuit board 13 is arranged in an interior ofthe power converter 1, which comprises a control circuit 200.

The other end of the extension cable 32 is formed with an appliance-sideconnector 33 which is engageable with a level-selecting terminal device4. The level-selecting terminal device 4 is formed with an outputterminal 41 for providing a selectable DC voltage output.

The extension cable 32 is releasably stowed in a cable-winding device 34to avoid entangling of the extension cable 32. A button 35 is providedon a top surface of the cable-winding device 34 for rewinding theextension cable 32.

At an appropriate position of the casing 1, there is disposed with adisplay device 5 which is capable to indicate/display the DC outputvoltage level provided via the output terminal 41 of the level-selectingterminal 4. When connecting to different level-selecting terminal device4, the display device 5 is able to indicate the real DC output voltagelevel.

The display device 5 comprises a plurality of indicators 51˜56 forshowing the DC voltage output through the output terminal 41 of thelevel-selecting terminal 4. Each of the indicators corresponds to adifferent DC output voltage level. The user can easily know from thelighting indicator 51˜56 the real DC voltage output of thelevel-selecting terminal device 4. Alternatively, the display device 5may comprise a liquid crystal display device 57 for indicating the DCvoltage output through the output terminal 41 of the level-selectingterminal device 4, as shown in FIG. 4.

Also referring to FIG. 2, which shows a block diagram of a controlcircuit of the power converter, the control circuit 200 comprises aDC-to-DC conversion circuit 61, a feedback circuit 62, a resistornetwork 62 and a DC voltage level indicating circuit 64.

The DC output terminals DC+, DC− of the rechargeable batteries 2 aredirectly coupled to the DC-to-DC conversion circuit 61 for supplyingpower. The rechargeable batteries 2 are charged by an AC power ACV via acharging circuit 21.

The output socket 12 comprises two primary, power terminals V10+, V10−and a plurality of secondary, level-selecting terminals V11, V12, V13,and V14. The resistor network 63 and the feedback circuit 62, which areconnected in series, are connected between the output socket 12 and theDC-to-DC conversion circuit 61 for generating a feedback signal Sf tothe DC-to-DC conversion circuit 35. The resistor network 36 is comprisedof resistors R11, R12, R13, and R14, which are in turn connectedrespectively to the level-selecting terminals V11, V12, V13, and V14 ofthe output socket 12.

The DC voltage level indicating circuit 64 is connected to thesecondary, level-selecting terminals V11, V12, V13, and V14 of the firstresistor network 63. The level-selecting terminal device 4 is alsocomprised of primary and secondary terminals V′10+, V′10−, V′11, V′12,V′13, and V′14, which are respectively connected to the primary andsecondary terminals V10+, V10−, V11, V12, V13, and V14 of the outputsocket 12, when the level-selecting terminal device 4 is connected tothe output socket 12 by means of the extension cable 32.

By selective use of different jump connection 42 between the secondaryterminals V′11, V′12, V′13, and V′14 and the primary terminal V′10−, adifferent resistance is observed in the resistor network 36, whichchanges the feedback signal Sf and thereby changes the output level ofvoltage at the output terminal V1+, V1− of the level-selecting terminaldevice 4. The output level of voltage at output V1+, V1− is displayed onthe display device 5.

Also referring to FIG. 3, a block diagram of the DC voltage levelindicating circuit 64 is shown. The DC voltage level indicating circuit64 comprises operational amplifiers 641, 642, 643, 644 each having afirst input connected to the level-selecting terminals V11, V12, V13,and V14 of the resistor network 63 whereby each operational amplifier641, 642, 643, 644 and the associated resistor R11, R12, R13, R14 formsa comparison circuit. Each operational amplifier 641, 642, 643, 644 hasa second input connected to a power source of +5V. Each operationalamplifier 641, 642, 643, 644 has an output coupled to and applying anoutput signal to a decoding circuit 645, which in turn generates outputsignals applied to and driving the indicators 51˜56. Thus, theindicators 51˜56 shows to a user the voltage level at the output V1+,V1−.

Also referring to FIG. 4, a power converter constructed in accordancewith a second embodiment of the present invention is shown. The secondembodiment is substantially identical to the first embodiment withreference to FIG. 1, except that the display device 5 comprises a liquidcrystal display device 57. The voltage level of the level-selectingterminal device 4 is displayed at the liquid crystal display 57.

A block diagram of a control circuit of the second embodiment is shownin FIG. 5. A microprocessor 58 is coupled, via any known interface, tothe resistor network 63 to detect the voltage level. The microprocessor58 decodes and calculates to generate a signal to control the liquidcrystal display 57 to display the voltage level as well as otherelectrical parameters. The DC voltage level indicating circuit 64 of thepower converter 100 is thus omitted here.

FIG. 6 shows a perspective view of a third embodiment of the powerconverter of the present invention. The third embodiment issubstantially similar to the first and second embodiments, and likereference numerals are used to identify elements that are similar oridentical in the embodiments. In the third embodiment, the casing 1 a isincorporated with a lighter plug 7 which is engageable with a standardcigarette lighter socket 7 (not shown) provided in an automobile orairplane. The casing 1 a is formed with a plurality of indicators 51˜56for showing the DC voltage output at the output terminal 41 of thelevel-selecting terminal device 4. Each of the indicators corresponds toa different DC voltage level. The user can easily know from the lightingindicator 51˜56 the real DC voltage output to the level-selectingterminal device 4. The casing 1 a also comprises a control circuit andDC voltage level indicating circuit similar to those shown in FIGS. 2and 3.

Please refer to FIG. 7, which is a perspective view of a fourthembodiment of the power converter of the present invention. The fourthembodiment is different from the third embodiment in that the indicators51˜56 are provided at the appliance-side connector 33. By means of theindicators 51˜56, the DC voltage output to the output terminal 41 of thelevel-selecting terminal device 4 is shown.

FIG. 8 is a perspective view of a fifth embodiment of the powerconverter. In this embodiment, the casing 1 b is formed with an AC plug8 for engaging to an AC socket or electrical main, such as a wall outlet(not shown). Preferably, the AC plug 8 comprises a plurality ofchangeable pins for plugging to different types of sockets and powersources e.g. 110V or 220V.

With reference to FIG. 9, a block diagram of the control circuit of thefifth embodiment is shown. The control circuit of the fifth embodimentis substantially similar to the control circuit of the first embodimentshown in FIG. 2. The control circuit 200 comprises a DC-to-DC conversioncircuit 61, a feedback circuit 62, a resistor network 63 and a DCvoltage level indicating circuit 64. The control circuit 200 furthercomprises a AC-to-DC conversion circuit 22 which converts the AC supplyfrom a power ACV into DC power that is then applied to the DC-to-DCconversion circuit 61. The power converter 100 comprises a controlcircuit 200 and a DC voltage level indicating circuit that issubstantially identical to that of the first embodiment.

The casing 1 b is formed with a plurality of indicators 51˜56 forshowing the DC voltage output to the output terminal 41 of thelevel-selecting terminal device 4.

FIG. 10 shows a perspective view of a sixth embodiment of the powerconverter of the present invention. In this embodiment, the extensioncable 91 has opposite ends forming an appliance-side connector 33 and adevice-side plug 9, respectively. The device-side plug 9 comprises aconventional AC plug for plugging to AC socket. The power converter 100comprises a control circuit that is substantially identical to thatshown in FIG. 2. The appliance-side connector 33 is engageable with alevel-selecting terminal device 4 for supplying a selectable DC voltagevia the output terminal 41. The appliance-side connector 33 is providedwith a plurality of indicators 51˜56 for showing the DC voltage outputto the output terminal 41 of the level-selecting terminal device 4.

Although the present invention has been described with reference to thepreferred embodiments thereof, it is apparent to those skilled in theart that a variety of modifications and changes may be made withoutdeparting from the scope of the present invention intended to be definedby the appended claims.

1-16. (canceled)
 17. A power converter comprising: a casing; at leastone rechargeable battery, which is disposed in an interior of the casingfor supplying a DC voltage; an output socket disposing at one side ofthe casing and connecting to a circuit board, which comprises twoprimary, power terminals and at least one secondary, level-selectingterminal; the circuit board disposing at the interior of the casing,which comprises a control circuit including a feedback circuit and aDC-to-DC conversion circuit, in which the feedback circuit is coupled tothe DC-to-DC conversion circuit and connected to the level-selectingterminal; a level-selecting terminal device, which is engageable withthe output socket and comprises two primary, power terminals and atleast one secondary, level-selecting terminal, and when thelevel-selecting terminal device is connected to the output socket, theprimary and secondary terminals of the level-selecting terminal deviceare respectively connected to the primary and secondary terminals of theoutput socket for receiving the selectable DC voltage therefrom andtransmitting the DC voltage through an output terminal of thelevel-selecting terminal device; a display device, which is connectedwith the control circuit to display the voltage level of the DC outputvoltage at the output terminal of the level-selecting terminal device.18. The power converter as claimed in claim 17, wherein the displaycircuit comprises a plurality of indicators, each of which correspondsto a different DC voltage level for indicating the output voltage levelfrom the output socket.
 19. The power converter as claimed in claim 17,wherein the display circuit comprises a liquid crystal display unit fordisplaying the output voltage level from the output socket.
 20. Thepower converter as claimed in claim 17, wherein the casing furthercomprises an input socket, with which a plug of a power cord connectingto a power source is engageable for charging the rechargeable battery bya charging circuit.
 21. The power converter as claimed in claim 17,wherein the power converter further comprises a connector connecting toa plug via an extension cable, the plug being engageable with the outputsocket of the casing and the connector comprising two primary, powerterminals and at least one secondary, level-selecting terminal incorresponding to the primary and secondary terminals of the outputsocket.
 22. The power converter as claimed in claim 17, wherein eachlevel-selecting terminal of the output socket being connected to thefeedback circuit by a resistor, and the level-selecting terminal devicecomprises a plurality of jump connections, wherein by selective use ofthe jump connection, a different resistance is observed which changesthe feedback signal and thereby changes the output level of voltage atthe output terminal of the level-selecting terminal device.
 23. Thepower converter as claimed in claim 17, wherein the display device isdisposed on a top of the casing.
 24. The power converter as claimed inclaim 21, wherein the display device is disposed on the connector.
 25. Apower converter comprising: a casing; a DC power socket, which isincorporated with the casing for receiving a DC power therefrom; anoutput socket disposing at one side of the casing and connecting to acircuit board, which comprises two primary, power terminals and at leastone secondary, level-selecting terminal; the circuit board disposing atthe interior of the casing, which comprises a control circuit includinga feedback circuit and a DC-to-DC conversion circuit, in which thefeedback circuit is coupled to the DC-to-DC conversion circuit andconnected to the level-selecting terminal; a level-selecting terminaldevice, which is engageable with the output socket and comprises twoprimary, power terminals and at least one secondary, level-selectingterminal, and when the level-selecting terminal device is connected tothe output socket, the primary and secondary terminals of thelevel-selecting terminal device are respectively connected to theprimary and secondary terminals of the output socket for receiving theselectable DC voltage therefrom and transmitting the selectable DCvoltage through an output terminal of the level-selecting terminaldevice; a display device, which is connected with the control circuit todisplay the voltage level of the DC output voltage at the outputterminal of the level-selecting terminal device.
 26. The power converteras claimed in claim 25, wherein the display circuit comprises aplurality of indicators, each of which corresponds to a different DCvoltage level for indicating the output voltage level from the outputsocket.
 27. The power converter as claimed in claim 25, wherein thedisplay circuit comprises a liquid crystal display unit for displayingthe output voltage level from the output socket.
 28. The power converteras claimed in claim 25, wherein the power converter further comprises aconnector connecting to a plug via an extension cable, the plug beingengageable with the output socket of the casing and the connectorcomprising two primary, power terminals and at least one secondary,level-selecting terminal in corresponding to the primary and secondaryterminals of the output socket.
 29. The power converter as claimed inclaim 25, wherein the output socket each level-selecting terminal of theoutput socket being connected to the feedback circuit by a resistor, andthe level-selecting terminal device comprises a plurality of jumpconnections, wherein by selective use of the jump connection, adifferent resistance is observed which changes the feedback signal andthereby changes the output level of voltage at the output terminal ofthe level-selecting terminal device.
 30. The power converter as claimedin claim 25, wherein the display device is disposed on a top of thecasing.
 31. The power converter as claimed in claim 28, wherein thedisplay device is disposed on the connector.
 32. A power convertercomprising: a casing; an alternating current plug, which is incorporatedwith the casing and is engageable with an AC socket for receiving an ACpower therefrom; an output socket disposing at one side of the casingand connecting to a circuit board, which comprises two primary, powerterminals and at least one secondary, level-selecting terminal; thecircuit board disposing at the interior of the casing, comprising acontrol circuit and an AC-to-DC conversion circuit, in which the controlcircuit includes a feedback circuit and a DC-to-DC conversion circuit,and the feedback circuit is coupled to the DC-to-DC conversion circuitand connected to the level-selecting terminal, and the AC-to-DCconversion circuit converts the AC power from AC socket into DC power; alevel-selecting terminal device, which is engageable with the outputsocket and comprises two primary, power terminals and at least onesecondary, level-selecting terminal, and when the level-selectingterminal device is connected to the output socket, the primary andsecondary terminals of the level-selecting terminal device arerespectively connected to the primary and secondary terminals of theoutput socket for receiving the selectable DC voltage therefrom andtransmitting the selectable DC voltage through an output terminal of thelevel-selecting terminal device; a display device, which is connectedwith the control circuit to display the voltage level of the DC outputvoltage at the output terminal of the level-selecting terminal device.33. The power converter as claimed in claim 32, wherein the displaycircuit comprises a plurality of indicators, each of which correspondsto a different DC voltage level for indicating the output voltage levelfrom the output socket.
 34. The power converter as claimed in claim 32,wherein the display circuit comprises a liquid crystal display unit fordisplaying the output voltage level from the output socket.
 35. Thepower converter as claimed in claim 32, wherein the power converterfurther comprises a connector connecting to a plug via an extensioncable, the plug being engageable with the output socket of the casingand the connector comprising two primary, power terminals and at leastone secondary, level-selecting terminal in corresponding to the primaryand secondary terminals of the output socket.
 36. The power converter asclaimed in claim 32, wherein each level-selecting terminal of the outputsocket being connected to the feedback circuit by a resistor, and thelevel-selecting terminal device comprises a plurality of jumpconnections, wherein by selective use of the jump connection, adifferent resistance is observed which changes the feedback signal andthereby changes the output level of voltage at the output terminal ofthe level-selecting terminal device.
 37. The power converter as claimedin claim 32, wherein the display device is disposed on a top of thecasing.
 38. The power converter as claimed in claim 35, wherein thedisplay device is disposed on the connector.
 39. A power convertercomprising: an output socket comprising two primary, power terminals andat least one secondary, level-selecting terminal; a circuit boardcomprising a control circuit including a feedback circuit and a DC-to-DCconversion circuit, in which the feedback circuit is coupled to theDC-to-DC conversion circuit and connected to the level-selectingterminal; a level-selecting terminal device, which is engageable withthe output socket and comprises two primary, power terminals and atleast one secondary, level-selecting terminal, and when thelevel-selecting terminal device is connected to the output socket, theprimary and secondary terminals of the level-selecting terminal deviceare respectively connected to the primary and secondary terminals of theoutput socket for receiving the selectable DC voltage therefrom andtransmitting the DC voltage through an output terminal of thelevel-selecting terminal device; a display device, which is connectedwith the control circuit to display the voltage level of the DC outputvoltage at the output terminal of the level-selecting terminal device.40. The power converter as claimed in claim 39, wherein the displaycircuit comprises a plurality of indicators, each of which correspondsto a different DC voltage level for indicating the output voltage levelfrom the output socket.
 41. The power converter as claimed in claim 39,wherein the display circuit comprises a liquid crystal display unit fordisplaying the output voltage level from the output socket.